General Category > Unofficial F/A-18 Acceleration Pack board
Flight Model Comparisons
MikeB54:
"Realistic" is exactly what Sludge is trying to do with his Auto Pitch mod. What is supposed to happen is that on a cat launch the nose will pitch up, hands off, to 10 degrees. The velocity vector will trail it, but catch up as the airspeed increases.
One big disadvantage we have is that the Hornet auto trims to 1G flight with weight off the wheels. The VRS SuperHornet does that but the Acceleration Hornet doesn't. I don't know if that is something that can be added or not but if it could it would make things a lot easier.
By the way, I have been playing around with the TrimEffectiveness settings in the aircraft.cfg. A setting of about 0.7 (I have to fine tune that some more) seems to work very well. On field takeoffs with the trim set to 12 NU the jet will fly off on its own at about 170 kts which Chris says is realistic. Cat launches with trim set to 15 NU, which is as high as it will go, aren't bad but need some tweaking. It also helped with the pronounced pitch up I was experiencing when rolling out of turns. Keep in mind that when I was testing this I had renamed the base.xml file in the Sludge Hornet to temporarily disable the auto pitch. The downside is that since there is no auto trim you really need trim buttons configured on your stick because you will be using them a lot.
On a slightly different topic, cruise performance is off, too. Cruise AoA isn't specified in the NATOPS. It mentions 2 settings; dash AoA of approximately 2.5 or lower and cruise AoA of greater than 2.5. I set up a test where I was cruising at FL200 with an AoA of 3.2 and was only doing 0.45M. Chris didn't have a specific number for me but said that was way too slow especially since I only had about 5000 pounds of fuel on board at the time.
Mike
Sludge:
Mike...
Yeah, the auto trim is something that is being worked on by JIMI. He is definately doing alot of the ground work on that one... it's been testing well and might get adopted into the Sludge at some point. Will keep you updated on the progress there.
The trim stuff is something I'm debating about fixing the auto-elevator or just leaving it all to the pilot. Right now, I re-tweaked the Sludge to get closer to the default so that I can fix the "pitch up on roll out". Am getting a hold on the "why" just have to run a few more tests to make sure thats the cut-n-dry reason its pitching up. Here's a good question to ask Chris: on the auto-trim cat launch, does the trim "disengage" from its auto setting once the pilot takes over? Meaning... REAL WORLD... Hornet set at 12 NU TRIM, you do the cat shot and grab the stick, does the FCS sense this and dial the trim back down? This will help me determine if I can make an XML that would disengage the trim and go to an UA auto-trim flight state.
Also, the problem with cruise performance and speeds is also one of the biggest limitations of FSX. FSX accounts for pressure altitude but doesnt CORRECTLY compensate for density altitude. What you end up getting is decent performance up to 8-10k' AGL but then the power/altitude thrust curve falls off way beyond real-world. One of the things I've tried to do was get more real-world mid/high altitude performance from the Hornet, so that you can dogfight in the 20-30k range but with this FSX limitation it's very difficult to overcome. When I looked at the charts, the Hornet is supposed to be at max cruise efficiency around 36k. But again, because of the FSX pressure vs density altitude miscalculation problem, the default (and Sludge) dont fly well (underpowered) in that airspace regime. So that will be a down-the-line fix, when I can full wrap my head around that specific topic and the fixes given out at FSDEVELOPER.com site.
Later
Sludge
jimi08:
Hey Mike,
As Sludge mentioned, I have been working on a somewhat elaborate Pitch Auto Trim system. It first trims to 1.0 G and then to 0 pitch rate. It only does this once the the simulator has sensed that the pilot is not providing any pitch input (i.e. flight stick has been released). Once pitch input has been sensed from the pilot, the trim zeros out and allows the pilot to control the Hornet as normal, and then goes back to re-trimming the aircraft once controls are released again. I designed the autotrim system to only work when the landing gear is retracted, allowing the pilot to have full control of the trim for takeoff and landing operations.
Like the SLUDGE, my variant is a work in progress.
If you have the time, it would be great if you can check it out and give me some honest feedback (and anyone else for that matter).
Here's the link if you are interested.
http://www.fsxblueangels.com/forum/viewtopic.php?f=91&t=4584
GOONIE:
Regarding the trim, one feature I noticed in the super hornet sim, is when you adjust trim with your thumb on the stick, the trim value appeared on the HUD briefly. This was a helpful feature when in the pattern and getting the proper trim value set.
Mike, can you ask your son if the trim value shows up on the Charlie Hornet's HUD?
To the HUD developers on this forum, I think adding this feature to the HUD would be helpful in the pattern, instead of having to look for the trim setting on the checklist page, and since we don't have "seat of the pants" feel or stick force feedback in FSX or sim flying.
The trim value appeared on the HUD only when you changed it, displayed for about 2 seconds above the tacan distance in the lower right.
-CAPT
SUBS17:
--- Quote from: jimi08 on December 31, 2011, 11:54:28 am ---Hey Mike,
As Sludge mentioned, I have been working on a somewhat elaborate Pitch Auto Trim system. It first trims to 1.0 G and then to 0 pitch rate. It only does this once the the simulator has sensed that the pilot is not providing any pitch input (i.e. flight stick has been released). Once pitch input has been sensed from the pilot, the trim zeros out and allows the pilot to control the Hornet as normal, and then goes back to re-trimming the aircraft once controls are released again. I designed the autotrim system to only work when the landing gear is retracted, allowing the pilot to have full control of the trim for takeoff and landing operations.
--- End quote ---
Thats how the FCS works in PA mode it requires more trim input but in UA mode the trim requirement is less as the FBW does it for you IRL. Its when you have dropped a store, fuel balance etc. That you actually require small amounts of trim from what I understand. FBW is not 100% auto trim in the case of Hornets/F-16 and Superhornet. We've had quite a few debates on this on other forums as to how much trim input is required and a few actual pilots have mentioned how much they had to input and when.
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